System and method to track inventory using RFID tags

ABSTRACT

System and method for tracking inventory of a multiplicity of products. First RFID tags are associated with respective products or groups of products. Second Active RFID tags are associated with respective first containers for the multiplicity products. A third Active RFID tag is associated with a second container for the first containers. First RFID tags broadcast their respective identifications. Second Active RFID tags hash the identities of the first RFID tags within their respective first containers and broad their hashed values. Third Active RFID tag hash the hashed values broadcast by the second Active RFID tags. An expected value is compared to a result of the third Active RFID tag hashing the hashed values broadcast by the second Active RFID tags.

FIELD OF THE INVENTION

The present invention relates generally to inventory tracking systems,and more particularly to an inventory tracking system using RFID tags.

BACKGROUND

Active RFID tags are well known today. For example, the Matrics Groupmanufactures “MicroSensys (tm)” Active RFID tags, and KSW Microtecmanufactures “Smart Active Label (tm)” Active RFID tags. An Active RFIDtag includes a small battery, and transmits RF signals via an integralantenna. The battery adds significant cost to the Active RFID tag. TheActive RFID may be preprogrammed with an identity that represents theidentity of the product which bears the RFID tag. The transmitted RFsignals typically include the identity of the Active RFID tag. If theActive RFID tag includes data such as a recorded temperature, the ActiveRFID tag may transmit the data as well. An Active RFID tags caneffectively transmit to a receiver up to 100 meters away.

Passive RFID tags are also well known today. A Passive RFID tag does notinclude a battery; instead, the Passive RFID tag has an integral antennawhich receives RF signals from an Active RFID tag or remote transceiver.The transmitted RF signals power the Passive RFID tag, i.e. the PassiveRFID tag captures the energy of the RF signals which it receives anduses the energy to drive transceiver and other circuitry on the PassiveRFID tag. The transceiver circuitry on the Passive RFID tag transmitsthe identity coded into the Passive RFID to identify the product whichbears the Passive RFID tag. The Passive RFID tag may also include amemory to store any type of information transmitted by the Active RFIDtag or other remote transceiver. Typically, Passive RFID tags have arange of about three meters.

A known remote transceiver reads the identity information broadcast bythe Passive RFIDs or Active RFIDs. The remote transceiver can read RFIDtags on packages contained in a box to determine what packages the boxcontains or to confirm that the packages are all there. Also, the remotereaders can read RFID tags on packages at a cash register to determinean amount to charge to the customer (as does a known bar code reader).Also, the remote readers can detect packages at a store exit which bearRFID tags which have not been “disabled” at a cash register, and therebydetect shoplifters.

An object of the present invention is to track inventory such as boxesand packages within the boxes.

Another object of the present invention is to track inventory of boxesand packages within shipping containers.

SUMMARY OF THE INVENTION

The present invention resides in a system and method for trackinginventory of a multiplicity of products. First RFID tags are associatedwith respective products or groups of products. Second Active RFID tagsare associated with respective first containers for the multiplicityproducts. A third Active RFID tag is associated with a second containerfor the first containers. First RFID tags broadcast their respectiveidentifications. Second Active RFID tags hash the identities of thefirst RFID tags within their respective first containers and broadcasttheir hashed values. Third Active RFID tag hash the hashed valuesbroadcast by the second Active RFID tags. An expected value is comparedto a result of the third Active RFID tag hashing the hashed valuesbroadcast by the second Active RFID tags.

In accordance with features of the present invention, the first RFIDtags are Passive RFID tags and the second Active RFID tags are attachedto packages containing each product or group of products.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a block diagram of an RFID inventory tracking system whichincorporates the present invention.

FIG. 2 is a block diagram of an Active RFID tag; such a tag is includedwithin or attached to each box, each pallet and each shipping containerof the RFID inventory tracking system of FIG. 1.

FIG. 3 is a block diagram of a Passive RFID tag within each packagewithin the RFID inventory tracking system of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail with reference tothe figures. FIG. 1 illustrates an RFID inventory tracking systemgenerally designated 10 according to the present invention. In theillustrated embodiment, system 10 is used in a shipping container 11containing a multiplicity of pallets 13 a,b, and a plurality of boxes 15and 17 on pallet 13 a, and a plurality of boxes 19 and 21 on pallet 13b. In the illustrated example, there are just two boxes on each pallet;however, this is just to simplify the explanation of the presentinvention. Typically, there are many more boxes on each pallet. Withinbox 15 are a multiplicity of packages 115 a,b,c, within box 17 are amultiplicity of packages 117 a,b,c, within box 19 are a multiplicity ofpackages 119 a,b,c and within box 21 are a multiplicity of packages 121a,b,c. In the illustrated example, there are just three packages in eachbox; however this is just to simplify the explanation of the presentinvention. Typically, there are many more packages in each box.

Active RFID tags 33 a,b are attached to pallets 13 a,b, respectively. Inthe illustrated embodiment, packages 115 a,b,c (containing products, notshown) include respective Passive RFID tags 215 a,b,c, packages 117a,b,c (containing products, not shown) include respective Passive RFIDtags 217 a,b,c, packages 119 a,b,c (containing products not shown)include respective Passive RFID tags 219 a,b,c and packages 121 a,b,c(containing products not shown) include respective Passive RFID tags 221a,b,c. The Passive RFID tags can be attached to the respective packagesby sticky labels that contain flat RFID tags. Alternately, the productsthemselves within the packages can bear the Passive RFID tags.Alternately, the products themselves bear the Passive RFID tags, andthere are not packages at all. Instead, the products are lumped into theboxes. Boxes 15, 17, 19 and 21 include respective Active RFID tags 315,317, 319 and 321. The Active RFID tags can be attached to the respectiveboxes by adhesives or embedded within the container walls. There is alsoan Active RFID tag 400 attached to container 11. By way of example,container 11 is a shipping container such as that commonly found on aneighteen wheel truck or on a flat bed car of a train. By way of example,Active RFID tag 400 is attached to the underside of a ceiling ofcontainer 11.

Active RFID tag 315 transmits RF signals to Passive RFID tags 215 a,b,c(and incidentally to other Passive RFID tags in the vicinity). The RFsignals provide power to operate the Passive RFID tags 215 a,b,c andidentify the Active RFID tag 315. After authenticating the source of theRF information, each of the Passive RFID tags 215 a,b,c broadcasts itsidentification in return. Active RFID tag 315 has a list of all PassiveRFID tags within box 15. Active RFID tag 315 receives the identity ofeach Passive RFID tag 215 a,b,c, confirms that they are in the list ofall Passive RFID tags within box 15, and then hashes these identities.By way of example, the hashing comprises an XOR (exclusive or), Shift orother bitwise algorithm.

Active RFID tag 317 transmits RF signals to Passive RFID tags 217 a,b,c(and incidentally to other Passive RFID tags in the vicinity). The RFsignals provide power to operate the Passive RFID tags 217 a,b,c andidentify the Active RFID tag 317. After authenticating the source of theRF information, each of the Passive RFID tags 217 a,b,c broadcasts itsidentification in return. Active RFID tag 317 has a list of all PassiveRFID tags within box 17. Active RFID tag 317 receives the identity ofeach Passive RFID tag 217 a,b,c, confirms that they are in the list ofall Passive RFID tags within box 17, and then hashes these identities.By way of example, the hashing comprises an XOR (exclusive Or), Shift orother bitwise algorithm.

Active RFID tag 319 transmits RF signals to Passive RFID tags 219 a,b,c(and incidentally to other Passive RFID tags in the vicinity). The RFsignals provide power to operate the Passive RFID tags 219 a,b,c andidentify the Active RFID tag 319. After authenticating the source of theRF information, each of the Passive RFID tags 219 a,b,c broadcasts itsidentification in return. Active RFID tag 319 has a list of all PassiveRFID tags within box 19. Active RFID tag 319 receives the identity ofeach Passive RFID tag 219 a,b,c, confirms that they are in the list ofall Passive RFID tags within box 19, and then hashes these identities.By way of example, the hashing comprises an XOR (exclusive Or), Shift orother bitwise algorithm.

Active RFID tag 321 transmits RF signals to Passive RFID tags 221 a,b,c(and incidentally to other Passive RFID tags in the vicinity). The RFsignals provide power to operate the Passive RFID tags 221 a,b,c andidentify the Active RFID tag 321. After authenticating the source of theRF information, each of the Passive RFID tags 221 a,b,c broadcasts itsidentification in return. Active RFID tag 321 has a list of all PassiveRFID tags within box 21. Active RFID tag 321 receives the identity ofeach Passive RFID tag 221 a,b,c, confirms that they are in the list ofall Passive RFID tags within box 221, and then hashes these identities.By way of example, the hashing comprises an XOR (exclusive Or), Shift orother bitwise algorithm.

In an alternative embodiment of the present invention, Active RFID tags315, 317, 319, 321 could also be sent information from another reader asa measure of the products in the container. For example, a forkliftequipped with a reader can scan the products and hash the results as theproducts are loaded into the container or other storage unit. Then, theforklift reader sends the hashed results to the Active RFID tags 315,317, 319, 321.

Active RFID tag 315 broadcasts its identity and hashed value (based onthe hashing of the identities of Passive RFID tags 215 a,b,c). ActiveRFID tag 317 broadcasts its identity and hashed value (based on thehashing of the identities of Passive RFID tags 217 a,b,c). Afterauthenticating Active RFID tag 315 and Active RFID tag 317, Active RFIDtag 33 a hashes the hashed values broadcast from Active RFID tag 315 andActive RFID tag 317, and broadcasts the result along with the identityof Active RFID tag 33 a.

Active RFID tag 319 broadcasts its identity and hashed value (based onthe hashing of the identities of Passive RFID tags 219 a,b,c). ActiveRFID tag 321 broadcasts its identity and hashed value (based on thehashing of the identities of Passive RFID tags 221 a,b,c). Afterauthenticating Active RFID tag 319 and Active RFID tag 321, Active RFIDtag 33 b hashes the hashed values broadcast from Active RFID tag 319 andActive RFID tag 321, and broadcast the result along with the identity ofActive RFID 33 b.

After authenticating Active RFID tag 33 a and Active RFID tag 33 b,Active RFID tag 400 hashes the hashed values broadcast from Active RFIDtag 33 a and Active RFID tag 33 b. Active RFID tag 400 stores andperiodically broadcasts the hashed value that it computed from thehashed values broadcast from Active RFID tag 33 a and Active RFID tag 33b. (Known software allows the reader to “focus” its read attempts tocertain tags, for example, tags that begin with a certain alphanumeric.So if a shipping container had reusable tags for the pallets and theoverall reader, then those could be “focused.”)

When the shipping container 11 is initially loaded with pallets 13 a,band their boxes, the foregoing process is performed so that Active RFIDtag 400 computes the initial hash value. Then, the shipping container istransported on a tractor-trailer truck, train, ship etc., and when itreaches each destination an external RFID Reader (not shown) reads thehashed value computed by Active RFID tag 400 and compares it to anexpected hashed value. Preferably, the expected hash value is theoriginal hash value determined by Active RFID tag 400 at the initialpoint of departure. Thus, if one of the Passive RFID tags is not workingor missing at the initial point of departure, the expected hash valuecan still equal the actual hash value determined at the destination.Alternately, the expected hashed value is the hashed value that wouldresult if all of the Passive RFID tags on all of the packages arepresent (their Passive RFID tags worked and the Active RFID tagsproperly performed their hashing functions). In either case, theexternal RFID Reader can obtain the expected hash value from a network.If the actual hashed value broadcast by Active RFID tag 400 at thedestination matches the expected hash value, then the inventory in theshipping container is complete, i.e. nothing was lost during shipment.Because hashed values are broadcast by the Active RFID tags, theidentities of the packages are hidden. The foregoing process isperiodically repeated, so if some of the boxes are unloaded at adestination, new hashed values will be computed as described above forthe remaining boxes (and the packages within the remaining boxes), andActive RFID tag 400 will broadcast a new hashed value to the externalRFID Reader at the next destination. The external RFID Reader at thenext destination will receive (securely via a network, such as PGP, SSH,SCP, or HTTPS) the expected hash value for the remaining contents of theshipping container, and compare the expected hash value to thatbroadcast from Active RFID tag 400. If they match, then the inventory inthe shipping container is complete, i.e. nothing was lost duringshipment.

FIG. 2 illustrates each Active RFID tag 315, 317, 319, 321 and 400, inmore detail. Each Active RFID tag includes a battery 40 (such as aLithium-Ion battery), electronic transceiver circuitry 42, antenna 44,integrated circuit CPU 48, memory 49 (such as EEPROM or SRAM), andmemory 56 (such as EEPROM or SRAM). Each Active RFID tag also includes ahashing program 51 in memory 49 for execution on CPU 48. Transceiver 42includes a transmitter and a receiver coupled to antenna 44 to transmitand receive RF signals. An RF encoding program 50 in memory 49 executeson CPU 48 to initiate broadcast of the identity of the Active RFID tagto the Passive RFID tags. Memory 56 also stores the identity of ActiveRFID tag.

FIG. 3 illustrates each Passive RFID tag 215 a,b,c, 217 a,b,c, 219 a,b,cand 221 a,b,c in more detail. Each Passive RFID tag comprises knowntypes of CPU 68, memory 69 (such as EEPROM or SRAM), transceiver 62,antenna 64 for the transmitter and receiver, and memory 76 (such asEEPROM or SRAM). Memory 69 contains an RF authentication program 70which executes on CPU 68 to authenticate a received RF signal and, ifauthentic, respond with the Passive RFID's identification.

Based on the foregoing, a system and method for tracking inventory of acontainer have been disclosed. However, numerous modifications andsubstitutions can be made without deviating the scope of the presentinvention. For example, in system 10, the Active RFID tags 33 a and 33 bcan be omitted, Active RFID tag 400 hashes the hashed values broadcastby Active RFID tags 315, 317, 319 and 321, and the hashed valuedcomputed by Active RFID tag 400 and transmitted to an externaltransceiver is compared to an expected value similarly computed at theinitial point of departure. As another example, Active RFID tags couldsubstitute for the Passive RFID tags for items 115 a-c, 117 a-c, 119a-c, and 121 a-c in FIG. 1. In another embodiment of the presentinvention, there is another layer in the RFID hierarchy such that ActiveRFID tag 400 reads multiple tags (akin to Active RFID tags 33 a,b), butthese would read sections of tags on the Active RFID tag 33 level. Inother words, Active RFID tag 400 would read Active RFID tags 500-50Xwhich would read Active RFID tags 33 a-x which would read Passive RFIDtags 315, 317, 319. Therefore, the present invention has been disclosedby way of illustration and not limitation, and reference should be madeto the following claims to determine the scope of the present invention.

1. A method for tracking inventory of a multiplicity of products, firstRFID tags associated with respective products or groups of products,second Active RFID tags associated with respective first containers forsaid multiplicity products, and a third Active RFID tag associated witha second container for said first containers, said method comprising thesteps of: said first RFID tags broadcasting their respectiveidentifications; said second Active RFID tags hashing the identities ofsaid first RFID tags within their respective first containers andbroadcasting their hashed values; and said third Active RFID tag hashingthe hashed values broadcast by said second Active RFID tags.
 2. A methodas set forth in claim 1 wherein said second Active RFID tags areattached to packages containing said each product or group of products.3. A method as set forth in claim 2 wherein said first containers areboxes.
 4. A method as set forth in claim 2 wherein said second containeris a shipping container adapted for shipping as a body of a tractortrailer truck.
 5. A method as set forth in claim 1 further comprisingthe steps of: comparing an expected value to a result of the step ofsaid third Active RFID tag hashing the hashed values broadcast by saidsecond Active RFID tags.
 6. A method as set forth in claim 1 whereinsaid first RFID tags are Passive RFID tags.
 7. A system for trackinginventory of a multiplicity of products, said system comprising: firstRFID tags associated with respective products or groups of products,said first RFID tags including means for broadcasting their respectiveidentifications; second Active RFID tags associated with respectivefirst containers for said multiplicity products, said second Active RFIDtags including means for hashing the identities of said first RFID tagswithin their respective first containers and broadcasting their hashedvalues; and a third Active RFID tag associated with a second containerfor said first containers, said third Active RFID tag including meansfor hashing the hashed values broadcast by said second Active RFID tags.8. A system as set forth in claim 7 wherein said second Active RFID tagsare attached to packages containing said each product or group ofproducts.
 9. A system as set forth in claim 8 wherein said firstcontainers are boxes.
 10. A system as set forth in claim 8 wherein saidsecond container is a shipping container adapted for shipping as a bodyof a tractor trailer truck.
 11. A system as set forth in claim 7 furthercomprising: means for comparing an expected value to a result of saidthird Active RFID tag hashing the hashed values broadcast by said secondActive RFID tags.
 12. A system as set forth in claim 7 wherein saidfirst RFID tags are Passive RFID tags.